Apparatus for making silicone impregnated shielded lead



Sept. 3, 1963 B, c, MORETZ 3,102,299

APPARATUS FOR MAKING SILICONE IMPREGNATED SHIELDED LEAD Original Filed Dec. '7, 1956 5 Sheets-Sheet 1 INVENTOR.

BYNUM MORETZ ATTORNEYS Sept- 3, 1963 B. c. Mam-:fz 3,102,299

APPARATUS FOR MAKING SILICONE IMPREGNATED SHIELDED LEAD Original Filed Dec. 7, 1956 5 Sheets-Sheet 2 INVENTOR.

BYNUM MORETZ BY gw? ATTORNEYS sept. 3, 1963 B. C. MORETZ APPARATUS FOR MAKING SILICONE IMPREGNATED SHIELDED LEAD Original Filed Dec. 7. 1956 5 Sheets-Sheet 3 BYNuM MoREATz ATTORNEYS Sept. 3, 1963 B. c. MoRETz 3,102,299 APPARATUS FOR MAKING SILICONE IMPREGNATE'D SHIELDED LEAD Original Filed Dec. 7, 1956 5 Sheets-Sheet 4 I- 7 INVENTOR. E BYNuM MoRETz BY M.. I( l ATTORNEYS B. C. MORETZ APPARATUS FOR MAKING SILICONE IMPREGNATED SHIELDED LEAD Original Filed Dec. '7, 1956 5 Sheets-Sheet 5 Nm vm IN V EN TOR.

BYNUM MORETZ AT TOREYS UnitedStates Patent APPARATUS FOR `MAKING SILICNE" IMPREGNATED SHIELDED LEAD Bynum Clay Moretz, Bainbridge,`N.Y., assignor toTlie Bendix Corporation, a corporation of Delaware Original application Dec. 7, 1956, Ser. No. 627,045, lnow Patent No.\2,981,983, datedMay 2, 1961. Divided and this application Aug. 29, 1960, Ser. No. 52,6() 3` 9 Claims. (Cl. 12B- 5) This invention relates to the treatmenthof a porous` `Walled -iiexible tube lor conduit, `such as a ilexibley metal radio-shielding conduitand the like. Moreparticulfarly the invention relates to=an apparatusfor impregnating the walls ofsuch conduit with flexible' non-porous materials.

This application is a division of iapplication'Serial No.4

627,045, tiled December l7,1956, now PatentNdfZSL- `One of the objects `of the present invention is to provide a novel apparatus for impregnating porous-walled tubes. Y Another object `ofthe invention is to provide "an improved apparatusfor impregnatin'g tubes of the indicated character in a faster, more uniform manner.V

`A further object is to provide an improvedapparatus for impregnating porous-walled tubes whereby the tube is provided with a uniform smooth inner coatinghlayer, and the `necessity for draining the impregnati-ngfcompound fromthe impregnated tube-is eliminated: .l

Yet another object of the inventionlis `to provide an eimproved apparatus for making kan improved impregnated `flexible conduit by `subjecting the irripregnatingl compound in the tube sidewalls to pressure in two stages, and wherein the sidewalls of the tube are more uniform- 1y impregnated and are free `from voids, air bubblesgetc. t l

A still further object is to provide an improved sirnplied mold in which Vvthe conduit is positioned duringthe described impregnating` operation, "said mold including novelgaiting means, novel means for sealing the ends cf the` conduit to the walls of the mold cavity, Aandfnovel,

means for mountingva conduit bore-detinng mandrel r for reciprocation in an impregnated conduit.

Theabove `and further objeotsand novel features of thejinvention willv more ful-ly appear fromfthe following i detailed description when fthe same is read in connection withthe accompanyingdrawings. It is to be understood,

however, that the drawings are for the purpose ofiillustration only, and arenot intended as a ldefinition of the` `limitsof theinvention;

Inthe drawings, rwherein` like reference character-s refer to like parts throughout the several views, y

FIG. ll is ba view in elevation of atypical exible conduit whichmaybe treated in accordance with the invention, a central portion ofthe conduit being broken away,

i thetubesmaking up the portion o ithe conduit wall shown` at the left being progressively peeled or cut away;

FIG. 2` is a fragmentary view in elevation, generally corresponding `to the left hand portion `of FIG.`1, of` the conduit after an impregnating treatment in-accordance'with the invention; n

FIG; 3 is an enlarged fragmentary view in radial sec- `.tion through the conduit of FIG. 2, the section being taken along the line 3--3 of FIG. 2;

` FIG. 4 is a view in plan ofthe upper :and lower parts `of an embodiment of mold useful in carrying vout the `method of the invention, the upper mold part having been t lifted from the lower mold part and turned upside down. FIG. 5 isa View in vertical longitudinal axial ,section through the mold of FIG. 4 with the conduit being treated shown as positioned therein; n f

31,102,299 Patented Sept. 3, 1963 ICC FIG. 6 is a fragmentary View in vertical section through the mold and a conduit positioned therein, the section being takenfgenerally along the line 6-6 of FlG. 5; FIG; 7 -isaview in elevation of the assembled mold having a conduit to be treated contained therein, a portion vof a compound-supplying injection Vdevice being shown cooperating 'with the mold;

`FIG. 8 ,is an elevation of the mandrel empl fconduit-impr'egnatingmold; and f FIG. 9 is a somewhat schematic View, partially in side elevation and partially in section, of the impregnated conduit and m'old end block assembly during the iinal, mandrel advancing step.v 'f The embodiment of the conduit illustrated in the accompanying drawings, by way of example, is inthe form of yed in the "a `composite ,flexible metal-walled tube which is useful, lfor example, as a` -shield for conductors in the ignition system of an internalcombustion engine. When the metal wall `if the conduit is properly grounded,it forms an` eiiective shield'against the radiation of electromagnetic vibrations,

` setup by the ignition system, which would otherwise interfere with 'radio communication. When the conduit is employed with an airplane engine itis, of course, subjected to extremely adverse conditions including vibra-4 tion by wind current and engine operation, exposure to extremes of high and low temperatures, electrical corona,

grease, oil and moisture, as wellas wide variations in altitude. 1

The novel conduit construction of the invention will be more readily understood by a comparison of FlG. l wherein the assembled but unimpregnated conduit isj-designated 10, and FIG. 2, wherein the impregnated portion of the conduit shown is designated 21. As indicated in` FIG. 1, the conduit comprises a plurality of superposed telescoped tubes or sleeves made of braided wire,`three v beingrshown in the illustrative embodiment. vThe yinnermost of such tubes is designated 14, the intermediate wire tube being designated 16, and the outermost wire tube being designated 18.V The wire strands forming such tubes maybe braidedin a normal manner -to make up the tubes, and may be constitutedin various forms known to the art. In a preferred embodiment eachstrand is made up of about eight small wires laid side by side to simulate =a fiat strip. The tubes may be braided separately and inserted into Voneano'ther,or the larger diametered j tubes maybe braideddirectly on 'the smaller onesas a core'.` The smallest lor inner tube is generally braided on a solid removable core, which, of course, has vbeen removed from the illustrated conduit.

the right `in FIG.v 1.'

For the 'purpose of rendering the conduit moistureproof,V and'atthe sametime to provide a smooth, non.-

chating inner surface on the conduit to protect insulated wire passing therethrough against damage, the assembled H conduit member 10, made up of superposed tubes 1'4, `16,

and518, and, in the embodiment shown vhaving terminal fittings 11,11 connected thereto, is treatedfin a novel vmanner now to 'be described to provide therein a lining 28 and at the same time to provide thin 4layers 15 and 17, of

,the lining material, respectively, between adjacent layers of the inetal tubes" making upV the wall of the conduit. A thin coating 19 of suehcompound is :preferably also disposed uponl the outer surta-ce of metal tube 18, The layers 15,17 and19 are integrally connected to each other 'and to lining `28`through the porous braiding of the inter- Vening braided metal tubes.

amazes In addition to its non-chaling properties, the material of which lining 28 and layers 15, 17 and 19 is made should have good resistance to corona and should not contain volatiles for some uses. The lining material should be non-porous, iiexible and resilient. When set, said material should retain these properties when subjected to a wide range of temperatures and exposed to grease, gasoline, and moisture. A suitable material should also be tough and have the ability to conform to the braided metal tubing and withstand continual bending stresses. Elastomers, such as those having a polyvinylchloride base and silicone rubbers have been found suitable. One such silicone rubber or silastic compound is that sold under the trade-name Dow Silastic 132.

Another lining matenial which has been found suitable for use in flexible conduits for radio shielding aircraft engine ignition systems, for example, is a synthetic plastic material known in the .trade as a plastisol, i.e., a fluid dispersion of polyvinylchloride polymer in a plasticizer which may be converted by heat alone to an elastomeric vinyl compound. This material has a polyvinylchloride base with suitable plasticizers and a heat stabilizer. Suitable lillers may be used, if necessary, to vary the flow characteristics. A suitable composition consists of ten parts by weight of polyvinyl chloride, such as Geon #121, four parts of Rohm and Haas Paraplex C-50, two parts of Paraplex C-60 (a polyester) and two parts of a heat stabilizer consisting of a mixture of Paraplex C-50 and dibasic lead phthalate in equal parts. This material is prepared for application at normal room temperature. The Geon #121 should be in the form of a line powder, the plasticizers (Paraplex) are added in liquid form, and the heat stabilizing mixture is added in iinely powdered, well-mixed form. The ingredients are then mixed thoroughly, preferably under vacuum.

The impregnating compound such Aas silicone rubber or plastisol is applied to the above described structure (FIG. 1) in accordance with the novel method of the invention, one embodiment of which will now be described. Such method is conveniently carried out by use of the apparatus shown in FIGS. 4-9, inclusive.

Such mold, which is generally designated 24, is of the longitudinally divided type having a lower half and an upper half 26 which when assembled have an interface 23' disposed longitudinally of the mold and along planes diametral of the two confronting semi-cylindrical cavity portions 27 and 29 in the respective mold halves. Such two cavity portions form a cylindrical cavity 23 having a main extent with a diameter slightly greater than that of the outer braided tube 18 of conduit 10. Conduit 10 is disposed in the mold cavity in extended condition (being held in that condition and sealed at its ends to the cavity of the mold by means to be described and generally designated 30 at the left (FIG. 7) and 31 at the right.

When the mold has been assembled as shown in FIG. 7, with conduit 10 therewithin, it is then impregnated by a compound 22, such as those described above, supplied by `an injection cylinder shown generally at 32. Cylinder 32 has a piston 34 which is thrust downwardly by mechanism, not shown, to deliver plastic material 22 outwardly of cylinder 32 through nozzle '35. The outer end of the nozzle is tapered, and is received in e. similarly tapered opening 36 which is located at one end (the left in FIGS. 4, 5, and 7) of the upper portion 26 of the mold above the conduit-receiving cavity portion 29 therein. The thus delivered plastic material 22 is forced inwardly to a throat 38 in mold part 26 and thence longitudinally of the central passage in conduit 10, from which it ows outwardly through the porous sidewalls of the conduit into contact rwith the wall of the mold cavity, thereby filling the interstices in the tubes 14, 16, and 1S and forming the layers 15, 17, and 19'.

The construction of the means whereby the ends of the conduit 10, including terminal fittings 11 and 11', are positioned in Ithe mold cavity [and sealed to the walls thereof will be more readily apparent on consideration of FIGS. 4 and 5. As there shown, lower mold part 25 has an enlarged semi-cylindrical cavity 42 at the left therein coaxial of cavity portion 27, and a similar enlarged cavity 45 at the right end of such mold part. Upper mold part 26 is somewhat shorter than mold part 25, and is retained in position thereon by guide pins 12 receivable in holes 13 in the lower mold part. Upper mold part 26 has similar enlarged cavities 44 and 46 confronting cavities 42 and 45, respectively, in mold part 25. The enlarged cylindrical cavities thus provided at the ends of the conduit-receiving cavity 23 have diameters such that they freely receive the nuts 51 and 54 disposed on sleeve members 11 and 11', respectively, of the two terminal members of the conduit (FIG. l). A block 47 is slidably mounted in the left enlarged cavity, and a cylindrical block 49 is slidably mounted in the right enlarged cavity. The slidable blocks 47 and l49 provide means whereby the ends of the conduit are suitably positioned -within the mold cavity 23 and are sealed to the wall of such mold cavity. The conduit holding means includes an externally threaded nipple 50 disposed on the inner face of block 47 coaxial with the conduit-receiving cavity 23, and a similar nipple 52 disposed on the inner tace of block 49. The outer ends of the conduitreceiving cavity 23 are provided with shallow counterbores which snugly receive, respectively, sleeve portions 1.1 and 11' of the two terminal fittings on the conduit. Mold part 25 is provided with tleft and right shallow counterbore portions 55 and 57, and mold part Z6 is provided with shallow counterbore portions 56 and 59, such coun- 4terbore portions cooperating to form the aforesaid counterbores receiving the sleeve portions of the terminal fittings on the conduit.

'Ilhe upper mold part 26 is provided with a sprue bushing 72 at its left hand end (FIGS. 4, 5, -and 7) above block 47, the bushing having the above-mentioned bell mouth 36 and throat 38 therein. A plug 74, aligned with bushing 72, extends upwardly through mold part 25. The upper and lower inner surfaces of block 47 are at, as shown at 75 and 76, respectively, and abut the inner ends of bushing 72 land plug 74, whereby the block 47 is retained from rotation about its axis within its enlarged cavity in the mold 24.

Block 47 has a vertical passage 77 therein aligned with the inner end of the throat in bushing 72, said passage communicating with `a horizontal passage 79 extending to the right (FIGS. 4, 5, and 7) through nipple 50 into communication with the central passage in a conduit 10 held within mold cavity 23 by mounting means 30 and 31. In accordance with the invention, impregnating compound is lirst injected under pressure within a conduit 1G mounted in mold 24 so as completely to lill the central passage in the :conduit and the interstices in the sidewall of the conduit, after which the excess compound is forced 0r ejected from the central passage in the treated conduit. During such first step, the central passage 65 in block 49 is closed -by the nose `60 of mandrel 61, such mandrel being retracted to the position shown in FIG. 5 during hetinitial step of injecting plastic material into the con- Because of the very substantial pressures developed internally of the conduit during injection of plastic material 22 lby cylinder 32, it is desirable positively to back up blocks 47 and 49, thereby to prevent undesirable elongation of the conduit in the mold. Block 47 is backed up by a vertical flange member 40 affixed to the left hand end of the mold part 25 and overlying a portion of mold part 26 when a mold is assembled. Mold part 25 has a block 41 attached to the right hand end thereof, block 41 having two spaced upstanding ears 66 which form the outer terminus of the cavity 45. The central space 67 betweenthefears `66 provides a passage for the Vrecerption" portion of a block 70 affixed to the right hand end of upper mold Apart 26. As will be `apparent in FIGS. 5, 7

and 9, the assembled mold halves rare thus accuratelyheldagainst longitudinal movement with respect to each other and provide rigid abutmentswhich prevent the moving apart of blocks 47 and 49.` 'i i The :above mentioned mandrel 61 is shown most clearly in FIG. 8. Rearwar'dly of nose portion 60, the mandrel .is-of reduced diameter at 62, and rearwardly of portion `621`has a larger diameter, lining smoothing portion 63. v Thek mandrel is .reciprocated longitudinally of the cavity 23 `in the mold by la hydraulic ram ,64, generally shown in FIG. 9.. v y n i y f It will Ibe'assumed that the conduit has been assembled as shown in PIG. v`l, and that the parts thereof are clean `and dry. It will also be assumed that the upper mold part 26 has rbeen removed from lower mold part 2S, mandrel 61 has been retracted from block 49, and blocks 47 and `49 have `been lifted-from bottom mold part 25.

The conduit .isimpregnated as follows: An untreated conduit 10has its`nut `51 of fitting 11 screwed home on threadednipple Sil, andnut54 is screwed home on threaded nipple 52. The blocks 47 [and 49, and conduit 10, now assembled :as a unit, are lowered intoplace in the cavity in lower mold half 29 so that the conduit lies in mold cavityportion 27, the sleeve portions of the termin-al fittings lie in they-respective counterbores at the ends of the mold cavity, and the assembled nuts 51 and 54 and blocks `47 and 49 lie within enlarged cavity portions 42 and 44 of the lower mold-half. The upper mold-half 26 is then assembled upon the lower mold-half, and the mandrel `61 is -advanced by nam `64 to the position shown in FIG. 5 wherein its nose portion 60 effectively blocks passageS.

Impregnating material 22 may now be` introduced into `the mol-d lby presentinginjection,` cylinder 32 thereto, as

indicated in FIG. 7, and then thrustingpiston 34 thereof downwardly until material 22 has filled the central passage in the lconduit and the interstices or voids in the porous side Walls of the conduit fandvhas formedrthe layers v15, 17, and `'19 of such impregnating compound between the successive braided met-al tubes and on the exterior yof outer metal tube 18, respectively.

After the conduit has been iilled and the walls thereof impregnated, the thrusting force remains on piston 34. vMandrel 61 is now thrust to the left s'o as to travel thnough the central passage in the impregnated conduit 31, as in- E dicated in FIG. 9.` The nose portion 60 of `the mandrel t liminary :smoothing of layer 28. Portion 63 (of the mandrel `further smoothes the lining layer and forces outl through the conduitv wall any plastic material in excess of that required to form layer 28. After mandrel 61 has been fully advanced to the left,

`so that its nose lies beyond sleeve 11 of the left terminalr fitting, ram 64 is operated to retract the mandrel `to its starting position outwardly `of block 49.

iAs a result of such operations the plastic material torming the'layers `28, 15, 17, tand 19 `of the impregnated conduit is in effect double-worked, that is, the material is subjected initially to` appreciable pressure when it is first ,injected into the conduit, and is again subjected to pressure when the excess plastic `material is removed from `the conduit. As a result, 'all voids and air bubbles are removed from the wall of the conduit and the variouslplasducts at each side of the mold cavity, `the ducts being Iformed by shallow grooves 80 milled into the upper space of: mold part 2S. The resulting ductsare large enough to provide free egress of air lbut pass only small quantities of plastic lmaterial at each operation. Such discharged plastic material may be occasionally removed from the ducts in the mold when required.

The impregnated conduit 21 is then removed from the mold parts as follows: The mandrel 60 is preferably rst pulled out of the conduit 21, after which blocks 47 `and 49 with the attached impregnated conduit 21 are removed from mold part 26. Nut 51 is then unscrewed from nipple .'50, and 4nut 54 is unscrewed .from nipple 52 on block 49. The mold is then ready for the treatment of another conduit 10. y l Y i The thus impregnated `conduit 21A is then transferred to a-isuit'able -oven and baked for a suitable time and at a suitable temperature to set and cure the impregnating compound. Ordinarily a temperature of S40-360 F. and a baking time of 25-30 minutes 'are satisfactory for setting and curing the plastisol, lfor example. Thebaked lassembly is removed lfrom the oven'and allowed to cool to room tempenature, after which it is cleaned toV remove excess impregnating `compound therefrom yas required.

The present invention provides an improved moistureproof radio shielding conduit having a smooth inner `layer of plastic material of substantially uniform thickness, an improved simplied, reliable and eective method for fabricating such conduit, and a novel apparatus by which the method may be carried out.v The novel method makes it possible to make such conduits 'with assurance j as to the uniformity and highquality of the finished.

- subsequent advance of the mandrel into the mold insures that `the impregnating compound inthe tube sidewalls and tube lining isdense and lvoid-free. Further, use of such apparatus eliminates the necessity of any time-consuming operation of gravity draining excess compound from the impregnated conduit.

Although only single embodiments of the conduit, method, and apparatus of the invention have been illustrated in the accompanying drawings and described in the foregoing specication, it is to be expressly understood that thew invention is not limited thereto.

For example, -the apparatus is applicable to making conduits having a variety .of shapes; the `contour of the mold 'cavity and the shape of the mandrel may be altered as required by the shape of the conduit to be treated.

Various other changes may also be made, such as the with a fluid compound, comprising a mold having la cavity receiving the conduit in extended condition, means for substantially sealing the ends of the conduit to the wall of the cavity,means in the mold forming a passage for introducing impregnating compound into the passage in the conduit, and a mandrel mounted to be reciprocable in the conduit passage and introducible into the latter after the conduit has been filled vwith compound to expel excess compound from the conduit and to shape the compound remaining in the conduit into a smooth lining.

2. Apparatus for lining and impregnating the porous walls of a conduit having sleeve-like laterally imperforate terminal fittings and a. longitudinal passage therein with a sluggish compound, comprising a longitudinally divided mold having an elongated cavity receiving the conduit and the sleeves of the terminal fittings therein with `the conduit in extended condition, the cavity lying at the interface of the mold parts, means in the mold forming a passage for introducing impregnating cornpound into the passage Iin the conduit, means in the mold for substantially sealing the sleeves on vthe terminal fittings of the conduit to the ends of the wall of the cavity, and a mandrel mounted to be reciprocable in the conduit passage and introducible into the latter after the conduit has been filled with compound to expel excess compound from the conduit and to shape the compound remaining in the conduit into a smooth lining. p

3. Apparatus as defined in claim 2 for the impregnation of conduits having flanged terminal fittings wherein the sleeves of the terminal fittings are received within the outer ends of the mold cavity and the flanges on the fittings overlie the ends of the mold cavity.

4. Apparatus as defined in claim 3, comprising a block beyond each end of the mold cavity, the blocks being slidable toward and away from the respective ends of :the cavity, and each block having an inwardly facing abutment surface thereon adapted to engage the outer face of the flange.

5. Apparatus as defined in claim 4 for treating in the manner recited conduits having outwardly facing nuts on the terminal fittings inwardly of the anges on such fittings, wherein the mold has passages extending out.- wardly of and aligned with the ends of the mold cavity, said passages receiving the nuts on the respective terminal fittings.

6. Apparatus as defined in claim 5, comprising bosses on said blocks aligned with the ends of the mold cavity and threaded to receive the nuts of the terminal fittings thereon.

7. Apparatus for lining and impregnating the porous walls of a conduit having terminal fittings and a 1ongitudinal passage therein with a sluggish compound, cornprising block-like members in alignment with the conduit extended between them, a central passage in one of the members coaxial of the passage in the conduit, means including a feeding passage to introduce compound under pressure into the passage in the conduit, means selectively substantially to close the system composed of the members and the conduit except for said feeding passage, a central passage through the other of said members, and a mandrel introducible into the central passage in the conduit after the conduit has been filled with compound to expel excess compound from the conduit and to shape the compound remaining in the passage in the conduit into a smooth lining of substantially uniform thickness.

8. Apparatus for lining and impregnating the porous walls yof a conduit having terminal fittings and a longitudinal passage therethrough with a sluggish compound, comprising block-like members sealingly conneetable to the terminal fittings, means to hold the members in alignment with the conduit extended between them, central passages in the members coaxial of the passage in the conduit, means including a feeding passage in one of the members to introduce compound under pressure into the passage in the conduit, and a mandrel recipro cable in the central passage in the other of said members between a retracted position in which it closes .the passage in said other member and a position in which it extends through the passage in the conduit.

9. lApparatus as defined in claim 8 wherein the means for holding the members is a mold having a cavity embracing the conduit, and comprising means for holding the terminal fittings in substantially sealing contact with the ends of the cavity.

References Cited in the file of this patent UNITED STATES PATENTS 1,649,139 Sonen Nov. 15, 1927 2,561,351 Fentress- July 24, 1951 2,759,864 Kuehler Aug. 2l, 1956 

1. APPARATUS FOR LINING AND IMPREGNATING THE POROUS WALLS OF A CONDUIT HAVING A LONGITUDINAL PASSAGE THEREIN WITH A FLUID COMPOUND, COMPRISING A MOLD HAVING A CAVITY RECEIVING THE CONDUIT IN EXTENDED CONDITION, MEANS FOR SUBSTANTIALLY SEALING THE ENDS OF THE CONDUIT TO THE WALL OF THE CAVITY, MEANS IN THE MOLD FORMING A PASSAGE FOR INTRODUCING IMPREGNATING COMPOUND INTO THE PASSAGE IN THE CONDUIT, AND A MANDREL MOUNTED TO BE RECIPROCABLE IN THE CONDUIT PASSAGE AND INTRODUCIBLE INTO THE LATTER AFTER THE CONDUIT HAS BEEN FILLED WITH COMPOUND TO EXPEL EXCESS COMPOUND FROM THE CONDUIT AND TO SHAPE THE COMPOUND REMAINING IN THE CONDUIT INTO A SMOOTH LINING. 